Variable drawing curve



Feb. 2, 1960 J. w. JONES, JR

VARIABLE DRAWING CURVE Filed July 17, 1957 Fig! Fig. 3

John wdones, Jr

INVENTOR.

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min away 22m United States Patent '0 "ice VARIABLE DRAWING CURVE John W. Jones, Jr., Shelton, Conn.

Application July 17, 1957, Serial No. 672,475

2 Claims. (Cl. 33-177) This invention relates to drawing instruments and more particularly to an adjustable rule for use in drawing irregular curves and the like.

The primary object of the present invention resides in the provision of an adjustable rule for curved configurations which can be used to locate and connect points in the development of a curved line or surface.

The concept of the present invention resides in the provision of means for assuming and maintaining a curved shape conforming to the contours of a curve which a draftsman desires to reproduce without requiring the assistance of numerous French curves or the like. Utilized in the present invention is a flexible tube filled with a thermoplastic substance which will rigidify at room temperature to hold the tube in an adjusted shape.

Still further objects and features of this invention reside in the provision of a variable drawing curve that is simple in construction, easy to utilize and relatively inexpensive thereby permitting wide use and distribution,

These, together with the various ancillary objects and features of the invention which will become apparent as the following description proceeds, are attained by this variable drawing curve, a preferred embodiment being illustrated in the accompanying drawings, by way of example only, wherein:

Figure 1 is a plan view of the variable drawing curve comprising the present invention;

Figure 2 is a sectional detail view as taken along the plane' of line 22 in Figure 1 illustrating the manner in which the circular sectional shape of the curve permits convenient inking processes;

Figure 3 is a fragmentary sectional detail view as taken along the plane of line 33 in Figure 1 and illustrating in an enlarged scale one of the removable and replaceable plugs utilized in the invention;

Figure 4 is a plan view of the invention showing how the device is used for reproducing a curve; and

Figure 5 is a sectional detail View illustrating the construction of means for detachably holding the rule to a source of heat or for detachably holding the rule to a drawing board.

With continuing reference to the accompanying drawings wherein like reference numerals designate similar parts throughout the various views, reference numeral generally designates the variable drawing curve comprising the present invention. This drawing curve or adjustable rule comprises a tube 12 of rubber or other suitable flexible material which is comparatively strong and adapted to be filled with a suitable thermoplastic material 14 such as wax, parafiin, a synthetic resin or the like. The thermoplastic material 14 may be easily melted at a temperature above a normal room temperature yet will solidify quite rapidly at room temperature. A source of heat commonly available to draftsmen and others is the wall of a fluorescent lamp and it is Within the concept of the present invention for a draftsman to hold the tube against such a lamp for heating the thermoplastic 2,923,066 Patented Feb. 2, 1960.

material 14. Of course, the instrument may be detachably secured to the lamp by any suitable means.

Either or both ends of the tube 12 may be closed by removable plugs of the type shown best in Figures 1 and 4 and shown in section in Figure 3. The enclosure plugs as indicated at 18 and 20 may be formed from any suitable material such as plastics or the like and are externally threaded as at 22 for threaded engagement with the internally threaded portion 24 of the tube. Alternatively, if threaded connections are not desired, friction connections may be utilized.

As shown in Figure 5, the tube 12 may be provided with means such as a clamping plate 26 provided with suction cups 28 and 30 for holding the tube 12 against a surface as at 32 which may be either the drawing board, or may be a source of heat such as a fluorescent lamp generally provided in drafting areas and rooms. In lieu of the clamping arrangement shown, suitable clips may be provided that are secured to the tube 12 preferably adjacent the ends thereof so as to leave the maximum intermediate portion free for use, which clips may be secured to the plugs 18 and 20, or may be secured to one or both sides of the tube.

dn use, the tube is filled with a suitable thermoplastic material such as paraffin, wax, suitable synthetic plastic resins, or the like and then subjected to a temperature sufficiently high to melt the thermoplastic substance in the tube 12. This heat may be received from a fluorescent lamp or the like. The tube is then formed to the required shape and allowed to harden or solidify. A line may then be drawn with a pen or pencil held against one side of the device, the line resulting in a neat curve without the repeated use of portions of French curves.

It is preferred that the tube 12 be circular in section as shown in Figure 2, though other shapes may be equally adaptable. The use of the round shape 12 is advantageous for two reasons. The tube of circular shape will be least resistant to any type of folding or adjusting and in addition will provide a clearance as indicated at 40 which will reduce the possibility of blots due to ink creeping under the instrument when using an inking pen as indicated at 42. Further, it is to be noted that the circular tube 12 is probably the easiest to construct.

It is noted that the thermoplastic material 14 may be of the type that will solidify at room temperature or at temperature slightly thereabove and that the tube may or may not have protuberances that will help in holding the device in place. Further, after the thermoplastic material 14 has hardened, reverse portions of an irregular curve may be accurately drawn by merely reversing the device to draw the reverse portion of the curve.

It is to be noted that the term thermoplastic used herein is to be construed as to cover the use of pure elements such as lead, etc., eutectic alloys, compounds, thermoplastic resins and organic compounds.

One eutectic alloy has been found to be very successful. This consists of 44.7% bismuth, 22.6% lead, 8.3% tin, 5.3% cadmium and 19.1% indium. This alloy has a melting point of 117 F. and in contrast to various waxes this alloy will pass from a liquid to a solid quickly, retains its solid shape well, yet permits a small amount of bending for adjustments.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention ing an elongated hollow member formed from flexible material capable to withstand heat without melting in an operating temperature range between a low point at room temperature and a relatively higher point, said memher being adapted to be bent into a predetermined curvilinear form, a "filler of thermoplastic material provided in said member, said filler being solid at said low point of the temperature range whereby to retain said member in a predetermined form but being plastic at said relatively higher point of the temperature range whereby to permit variation in the form of said member by "bending, and closure plugs provided in the ends of said member, said plugs projecting beyond the ends ofthe member and having work engaging surfaces adapted for positioning of said member on a piece of work.

2. An adjustable curve drawing instrument comprising an elongated hollow member formed from flexible 'material capable to withstand heat without melting in an operating temperature range between a low point at room temperature and a relatively higher point, said member being adapted to be bent into a predetermined curvilinear form, a filler of thermoplastic material provided in said member, said filler being solid at said low'point of the temperature range whereby to retain said member in a predetermined form but being plastic at said relatively higher point of the temperature range whereby to permit variation in the form of said member by bending, and

References Cited in the file of this patent UNITED STATES PATENTS 1,136,295 Szilard Apr. 20, 1915 1,856,394 Letterman May 3, 1932 2,155,169 Moses Apr. 18, 1939 2,294,982 Hathaway Sept. 8, 1942 2,324,672 Bierman July 20, 1943 2,389,038 German Nov. 13, 1945 FOREIGN PATENTS 403,047 Italy Apr. 2, 1943 633,401 England Dec. 12, 1949 266,392 Switzerland Jan. '31, 1950 OTHER REFERENCES Popular Science, 'p. 98, October 1945. 

